1. Field of the Invention
This invention relates to an image reading head for an image scanner, a facsimile machine, or a copier. In particular, the present invention discloses a flat bed image reading head having a motor mounted thereon.
2. Description of the Prior Art
Flat bed image scanners are widely used today as periphery equipment for computers. A flat bed image scanner can rapidly scan a document, a magazine, a book, a graph or a picture for inputting images thereof into a computer for processing. A flat bed scanner has an optical reader, a driving mechanism, a processing circuit, a scanning window and a frame. Today, the trend is to make the scanner lightweight, thin, narrow and miniaturized. It is thus desirable that the optical reading mechanism and the driving mechanism occupy as little space as possible.
A conventional image reading head 199 is shown in FIG. 1 and includes: a light source 101, a series of reflecting mirrors 131, 132, 133, a lens 104 and an image sensor 105. The driving mechanism includes: a motor 107, a gear train 108, an idler 181, a closed-loop belt 109, and a sliding rail 110. The operation of the flat bed scanner is as follows: Referring to FIG. 1, a document D to be scanned is placed on top of a window 102. After the light source 101 illuminates the document D, the reflected light from the document D reflects from the reflecting mirrors 131, 132, 133 to the lens 104 to reach the image sensor 105. The image sensor 105 feeds image signals to an image processing circuit (not shown) for digitizing the signals, which are then fed to a computer for further processing. When the image sensor 105 completes a row of image signals, the driving mechanism moves the image reader to a next scanning area until the whole image is read.
Structurally, the advancing motor 107 and the gear train 108 are both fixed on the frame 112. The closed-loop belt 109 has one end connected to the gear train 108 and the other end connected to the idler 181. The closed-loop belt 109 is attached to the optical reading mechanism 199 to move the optical reading mechanism for effecting scanning action.
An object of this invention is to reduce the size of a flat bed scanner. Another object of this invention is to reduce the number of parts in a flat bed scanner to enhance the quality and to reduce the cost of the flat bed scanner.
These objects are obtained by combining the driving mechanism and the reading mechanism of the scanner into the same module. A fixture is mounted on the frame of the scanner. When the driving mechanism exerts a force on the fixture, the reaction causes the movable module to slide back and forth along a guiding portion and to scan the image to be read. The force from the movable module can be exerted on the fixture through a rack and pinion mechanism or through a friction wheel and friction tape.